1913] HOLM—PHRYMA LEPTOSTACHYA 300 
and the pericambium consists of a single stratum with no indication 
of developing cork or secondary cortex. But inside the pericam- 
bium the stele soon increases in thickness in the usual way, and 
already at the seedling stage. While no pith was observed in the 
primary root, this tissue is well represented in all the secondary 
roots, attains quite a considerable width in mature specimens, and 
contains deposits of starch. 
We have thus in Phryma two very distinct types of roots: 
nutritive roots, represented by the primary root; and a combina- 
tion of contractile and storage roots, as shown by the secondary 
roots with contractile exodermis and starch deposits in cortex 
and pith. 
The aerial stem 
In seedlings and in young, purely vegetative shoots the inter- 
nodes are cylindric, while in mature plants the stem becomes 
obtusely quadrangular and bisulcate to sharply 4-winged between 
the flowers. Furthermore, the internodes, at least in mature speci- 
mens, are more or less nodose, the node appearing some distance 
from the insertion of the leaves; these nodes are generally purplish, 
while the other parts of the stem are green. Similar nodes occur 
in various other plants, as among Labiatae, Scrophulariaceae, 
Polygonaceae, Acanthaceae, Caryophyllaceae, etc., and they may 
be located either directly at the insertion of the leaves or some dis- 
tance therefrom. According to Rtrzou,' the structure of the nodes 
in these families differs from that of the slender portion by the 
presence of more collenchyma, and of a less developed stereome; 
this author explains the function of these nodes to consist in facili- 
tating the bending of the stem, when such is necessary. In Phryma, 
however, the internal structure is almost identical throughout the 
internode, including the swelling, but the function seems to be the 
same as observed by Riirzou. 
The stem structure of Phryma in general is very uniform in 
young as well as in mature specimens, in the basal as well as in the 
apical internodes. The cuticle is thin and smooth in the sub- 
terranean stem portions, but becomes gradually thicker and longi- 
‘ Bot. Tidsskr. Kjbhvn 12:248. 1880-1881. 
